4 ms·

This is a C++-ism that has no place in C (and overused in C++).

pjmlp 4y ago
Even on C++, regardless of templates, most code doesn't need to be header only, other than laziness to properly learn how to work with compilers and build systems.
- eliasmacpherson 4y ago
  Hello. Forgive my ignorance and possible misunderstanding of your 'most code' qualifier. If I have a template header .hpp and I do not wish to specialize the template function bodies in a .cpp file, the template header function bodies must be declared in the .hpp, right?
  - pjmlp 4y ago
    Yes and no. Yes it needs to be on the header, however depending on what is the goal, many operations could eventually be delegated to helper functions or PIMPL classes, which aren't fully exposed on the header. And for the lucky users of VC++ 2022, there is also the option to use modules instead, where templates are then exposed via the module metada.
    - eliasmacpherson 4y ago
      Helper functions, PIMPL, that's all fine - the declaration and function body of the template is still defined in the .hpp. Whether all of the body of the template is also defined there was not my concern in asking. Thanks for your comment. I will have to dig in to modules in due course.
linkdd 4y ago
The lack of C or C++ build system makes me prefer header-only libraries, like nlohmann/json, entt, etc... I do also like easily embeddable tech like imgui, or lua, where you can simply copy the source code in your source tree.
- pjmlp 4y ago
  If anything there are plenty of options. How come we have managed during the last 40 years?
  - linkdd 4y ago
    I should have said: the lack of standardized build system. CMake is a pain, Bazel, vcpkg, autotools, plain old Makefiles, etc... All of them do not match the developer experience of npm, cargo, etc... Yeah we managed, I never said the opposite. I only talked about why I liked header-only libs: because I just copy/paste the source in my source tree, regardless of the build system I use. If I'm using CMake, and a library is using autotools, I'll have to rewrite the lib's build system, and maintain it. I'm too lazy for that.
    - pjmlp 4y ago
      You should have installed it already via the OS package system, or the modern alternative, conan/vcpkg.
  - flohofwoe 4y ago
    It was a massive pain in the butt in that time. Just try to intregrate a "standard library" like libjpeg or libpng into your cross-platform project. That's exactly why everybody has switched over to stb_image.h to quickly load image data without hassle.
    - pjmlp 4y ago
      Easy, have your "load/save_image" calls the OS provided APIs for image handling, while on UNIX assume the libjpeg-dev or libpng-dev are already installed via the OS package system, have the makefile targets adjusted as needed per platform. Nowadays, use cmake + conan/vcpkg as alternative as well. Do we need to spoon-feed everything?
      - flohofwoe 4y ago
flohofwoe 4y ago
The most popular "header only" (or rather "single file" libs) are mostly written in C though: https://github.com/nothings/stb https://github.com/nothings/stb Important difference to typical C++ header-only libs: STB style libs don't use the inline keyword, but instead place the implementation into an ifdef/endif block. It's really just for easier distribution and integration, and the difference to a single .h/.c pair isn't all that big. Definitely not big enough to get all riled up about it - the actual problem are libraries that come in dozens of source and header files and with their own build system files, or C++ libraries which put the implementation into inline code, like most C++ stdlib headers (because this increases compilation time for every file which includes such a header).

Even on C++, regardless of templates, most code doesn't need to be header only, other than laziness to properly learn how to work with compilers and build systems.

eliasmacpherson 4y ago
Hello. Forgive my ignorance and possible misunderstanding of your 'most code' qualifier. If I have a template header .hpp and I do not wish to specialize the template function bodies in a .cpp file, the template header function bodies must be declared in the .hpp, right?
- pjmlp 4y ago
  Yes and no. Yes it needs to be on the header, however depending on what is the goal, many operations could eventually be delegated to helper functions or PIMPL classes, which aren't fully exposed on the header. And for the lucky users of VC++ 2022, there is also the option to use modules instead, where templates are then exposed via the module metada.
  - eliasmacpherson 4y ago
    Helper functions, PIMPL, that's all fine - the declaration and function body of the template is still defined in the .hpp. Whether all of the body of the template is also defined there was not my concern in asking. Thanks for your comment. I will have to dig in to modules in due course.

linkdd 4y ago

The lack of C or C++ build system makes me prefer header-only libraries, like nlohmann/json, entt, etc... I do also like easily embeddable tech like imgui, or lua, where you can simply copy the source code in your source tree.

pjmlp 4y ago
If anything there are plenty of options. How come we have managed during the last 40 years?
- linkdd 4y ago
  I should have said: the lack of standardized build system. CMake is a pain, Bazel, vcpkg, autotools, plain old Makefiles, etc... All of them do not match the developer experience of npm, cargo, etc... Yeah we managed, I never said the opposite. I only talked about why I liked header-only libs: because I just copy/paste the source in my source tree, regardless of the build system I use. If I'm using CMake, and a library is using autotools, I'll have to rewrite the lib's build system, and maintain it. I'm too lazy for that.
  - pjmlp 4y ago
    You should have installed it already via the OS package system, or the modern alternative, conan/vcpkg.
- flohofwoe 4y ago
  It was a massive pain in the butt in that time. Just try to intregrate a "standard library" like libjpeg or libpng into your cross-platform project. That's exactly why everybody has switched over to stb_image.h to quickly load image data without hassle.
  - pjmlp 4y ago
    Easy, have your "load/save_image" calls the OS provided APIs for image handling, while on UNIX assume the libjpeg-dev or libpng-dev are already installed via the OS package system, have the makefile targets adjusted as needed per platform. Nowadays, use cmake + conan/vcpkg as alternative as well. Do we need to spoon-feed everything?
    - flohofwoe 4y ago

flohofwoe 4y ago

The most popular "header only" (or rather "single file" libs) are mostly written in C though: https://github.com/nothings/stb https://github.com/nothings/stb Important difference to typical C++ header-only libs: STB style libs don't use the inline keyword, but instead place the implementation into an ifdef/endif block. It's really just for easier distribution and integration, and the difference to a single .h/.c pair isn't all that big. Definitely not big enough to get all riled up about it - the actual problem are libraries that come in dozens of source and header files and with their own build system files, or C++ libraries which put the implementation into inline code, like most C++ stdlib headers (because this increases compilation time for every file which includes such a header).